4GB DOM might work if the OS and BIOS supports it though it's not mentioned in the THOL and I have never setup such scenario myself. You might as well have to confirm the compatibility since by default it comes with a 256MB DOM and in it's THOL (Tested Hardware and Operating System List) too, there are only two DOMs (Manufactured by PQI and Super Talent) of capacity 256MB that are certified to work with SS4200-EHW that you will find in the THOL I have attached on Pg. 5
For more information or support, follow the URL below and access the support website for SS4200-EHW:
After that, the four drives can use RAID5, so far in theory it seems valid however I still believe it could be different practically.
Go ahead with it and let us know what you experienced.
Intel Go Green, Save The Environment!
ss4200ehw_tholhw_10.pdf 159.4 K